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Thread: XT 130W PSU 120V tp 240V conversion, is it possible?

  1. #31

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    I didn't notice the changed diagram.
    The only issue is that most switches on the power supplies
    only switch the hot lead.
    If someone though turning it off at the switch was enough to
    poke around, a screwdriver or a ring on ones hand could find
    the 60V to ground.
    I do like the idea of the balanced voltage for other safety reasons.
    One could still manage to kill them selves with 60V but it is
    safer, as you mention.
    Dwight

  2. #32

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    Quote Originally Posted by mR_Slug View Post
    On second thoughts, would it not make more sense to bond the neutral of the 120V to the neutral of the 240V?

    Like this:
    Attachment 39695
    Umm, no. Like any other modern appliance, treat the Neutral on the incoming 240VAC as though it is "hot" because it's potential is not entirely certain. You might encounter a reverse-wired plug or overload at another point in the household circuit where that current raises the potential on N. Same reason why 240VAC appliances often switch both sides of the mains.

    On your schematic you need to remove the link between the incoming N and ground since that link is not part of the transformer assembly wiring between it's 240VAC plug and the two outgoing sockets. I also note there are no fuses and you might check to see if the transformer core is tied to ground as well.

  3. #33

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    Quote Originally Posted by paul View Post
    Umm, no. Like any other modern appliance, treat the Neutral on the incoming 240VAC as though it is "hot" because it's potential is not entirely certain. You might encounter a reverse-wired plug or overload at another point in the household circuit where that current raises the potential on N. Same reason why 240VAC appliances often switch both sides of the mains.

    On your schematic you need to remove the link between the incoming N and ground since that link is not part of the transformer assembly wiring between it's 240VAC plug and the two outgoing sockets. I also note there are no fuses and you might check to see if the transformer core is tied to ground as well.
    In the house we bought about 3 years ago, 20 percent of the sockets
    had neutral and hot swapped.
    Only 5 of them actually had the ground terminal connected.
    The seller recommended the contractor he'd been using. I asked
    if he'd upgraded the sockets to ground lead sockets.
    "He did a good job, didn't he!"
    was the response.
    Dwight

  4. #34

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    Well I got the new transformer. I folded over the pins, and soldered the two 6V windings together and did the same for the two 120V, giving a 240-12V configuration. Then I lightly touched one of the other pins, and it broke off immediately. So I managed to solder on a lead further back where the winding connected to the pin. It turned out that my measurements were wrong, and I needed to drill 1 new hole in the PCB. So anyway I did all this, got it all soldered in, was very pleased with myself, patted my self on the back, until I realized I'm an idiot.

    The negative side of the transformer doesn't connect directly to the negative coming in. It DID previously, but because I had removed the W23 jumper, now it just connects to the center of the two main caps. No one could have advised me of this, because my schematic was incorrect.

    So my intuition on reusing the 120V transformer was right, but my schematic tracing skills need more work.

    Anyway the end procedure is really quite simple, remove W23, solder in diodes at CR34 and CR35.

    Updated schematic
    finaldiag.jpg
    So now back to the filtering board. I can order some 0.1uF X2 caps, but would .22uF X2 275V work? I seem to have some left over from anther project, and I'm itching to get this finished.

    Tool transformer:
    Yes it does have fuses and switches, I just didn't add them to the diagram to make it simpler.
    Looking for: OMTI SMS Scientific Micro Systems 8610 or 8627 ESDI ISA drive controller, May also be branded Core HC, Please PM me if you want to part with one.

  5. #35

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    Quote Originally Posted by mR_Slug View Post
    I can order some 0.1uF X2 caps, but would .22uF X2 275V work?
    As long as it's marked X2 it should be fine.

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